Electrocatalytic and catalytic CO2 hydrogenation on ZnO/g-C3N4 hybrid nanoelectrodes

Abstract

The enhancement of efficiency of electrocatalysts towards the electrochemical reduction of CO2 reaction is always an exploring area of the present days. Herein, we have synthesized g-C3N4 and ZnO decorated g-C3N4 hybrid nanostructures by precipitation followed by calcination method. The as-synthesized nanostructures were well characterized by various spectroscopic techniques. X-ray diffraction suggests the synthesized material in the hexagonal Wurtzite structure. Whereas, scanning electron microscopy and transmission electron microscopy concludes the formation of a g-C3N4 layer with 23.7–71.4 nm and hexagonal decorated ZnO with 2.3 ± 0.5 nm, respectively. Furthermore, the electrochemical reduction of CO2 was observed at −0.504 V vs. RHE in the aqueous KHCO3 medium. The bulk electrolysis has been further carried out at −0.504, −0.734 and −0.934 V vs. RHE and obtained Faradic yield as 40.20, 53.60 and 80.99% respectively. Also, the same catalyst was used for the thermal reduction of CO2 in the batch reaction to confirm the activity and which gave excellent yield (10 mM) of the formate. Based on above investigations, a plausible reaction mechanism for hydrogenation of CO2 to formate synthesis over ZnO/g-C3N4 catalyst is also proposed. This methodology has been applicable for industrial applications for large scale production and hope will overcome the environmental and energy issues i.e., CO2 to formate as a fuel.